A publically available external defibrillator includes a detector used to detect a life threatening condition of a patient, a controller operating the defibrillator automatically and a therapy delivery circuit that delivers appropriate therapy. The body includes first and second electrodes for applying a voltage across both ends of passages of the wafer-shaped part to separate and remove the sample solution. The abrasive grains are firmly fixed to an end face portion excluding regions near an outer rim and near an inner rim of the end face and near the boundaries with the groove under the condition that, with respect to all the abrasive grains, skirts of a brazing material layer for holding the abrasive grains have a length one or more times an average grain size of the abrasive grains.